I hope not, my 10yr old DDs face after watching the trailer was hilarious though! She was shocked to see that last bit.
I am not a huge Star Wars fan that knows all the books and stories outside of the movies. They can't be twins, if she is as young as she seems in the sequence when she touches the lightsaber. Maybe siblings, or cousins. Personally I hope she isn't a Skywalker at all, just seems anticlimactic. But what do I know.